1. Field of the Invention
The present invention relates to a retaining device making use of a permanent magnet and, more particularly, to a magnetic retaining device improved to produce a large retaining power which withstands a comparatively heavy load even with a permanent magnet which has only a small magnetic flux density and, hence, a comparatively small magnetic attracting force.
2. Description of the Prior Art
Hitherto, various retaining devices making use of permanent magnets have been proposed and become known. In these known retaining devices, however, the retaining power which bears the load is derived solely from the magnetic attracting power produced by the permanent magnet. Therefore, in order to attain a large retaining power, it is necessary to employ a permanent magnet having a large magnetic attracting force. For these reasons, the conventional retaining devices incorporating permanent magnets could find only limited use and the price thereof is inevitably raised due to the use of expensive permanent magnet material having a large magnetic attracting force.